CN115779937B - Method for activating lattice oxygen on surface of perovskite oxide and application of method - Google Patents

Abstract

The invention discloses a method and application for activating lattice oxygen on the surface of perovskite oxide, and relates to the technical field of waste gas treatment. It includes preparing a perovskite catalyst precursor doped with fluoride ions through a hydrothermal method. After drying, Finally, it is calcined at a certain temperature for 2 hours at a certain heating rate to obtain the final perovskite catalyst; the present invention increases the lattice oxygen activity of the perovskite surface through fluoride ion doping, exhibits excellent catalytic activity, and is suitable for different applications. The catalytic performance of the fluorine-doped perovskite metal oxide prepared by the method is improved, the treatment method is simple, the catalytic combustion performance of the catalyst for VOCs is significantly improved, and the catalyst has good heat resistance and stable performance.

Description

A method and application for activating lattice oxygen on the surface of perovskite oxides

Technical field

The present invention relates to the technical field of waste gas treatment, and in particular to a method and application for activating lattice oxygen on the surface of perovskite oxide.

Background technique

In recent years, the type of ambient air pollution has gradually changed from soot pollution to regional composite pollution represented by atmospheric haze and increased oxidation (characterized by lung-transmitting particulate matter PM _2.5 and ozone respectively); considering the current atmospheric Pollution situation, VOCs pollution control is imminent.

For the treatment of VOCs exhaust gas, catalytic combustion is an economical and effective method. As a traditional organic waste gas treatment technology, catalytic combustion is currently one of the main technologies for VOCs treatment. The development of efficient and low-cost catalytic materials is the key to the popularization and application of this technology.

Perovskite oxide catalysts have attracted much attention due to their excellent heat resistance and structural stability. Currently reported perovskite oxide catalysts usually have catalytic activity under low temperature conditions that cannot meet the needs of industrial applications. Therefore, while maintaining the excellent heat resistance and structural stability of perovskite oxide materials, improving its low-temperature catalytic oxidation performance is the key for perovskite oxide catalysts to meet the needs of industrial applications.

Contents of the invention

The purpose of the present invention is to solve the technical problems existing in the prior art and provide a method and application for activating lattice oxygen on the surface of perovskite oxide.

In order to achieve the above objects, the present invention provides the following solutions:

The invention provides a method for activating lattice oxygen on the surface of perovskite oxide, which includes the following steps:

S1. First mix lanthanum nitrate and nitrate, add water to dissolve, then add complexing agent after complete dissolution, and finally add fluoride salt and stir;

S2. The stirred solution in S1 is subjected to a hydrothermal reaction. After the hydrothermal reaction is completed, dry it overnight to obtain the catalyst precursor;

S3. Calculate the catalyst precursor obtained in S2.

Preferably, the nitrate is cobalt nitrate, iron nitrate or manganese nitrate.

Preferably, the fluoride salt is cobalt fluoride, iron fluoride or manganese fluoride (where the sum of the amounts of metal ions in the nitrate and the metal ion species in the fluoride salt is 0.005 mol).

Preferably, the complexing agent is one or more of tartaric acid, citric acid and EDTA.

Preferably, the added amount of fluoride salt is 10%-50% of the amount of lanthanum nitrate substance.

Preferably, the hydrothermal reaction temperature is 160-200°C, and the hydrothermal reaction time is 10 hours.

Preferably, the calcination temperature is 700-1000°C and the calcination time is 2 hours.

Preferably, the heating rate during the calcination process is 2-10°C/min.

A perovskite oxide catalyst is obtained according to the method, and the perovskite oxide has a cubic structure of _ABO3 .

Application of the perovskite oxide catalyst in catalyzing the combustion of VOCs.

The invention discloses the following technical effects:

The reaction equipment of the invention is simple, the reaction time is short, and the reaction is easy to operate; the reaction raw materials are easy to obtain, and the cost of raw materials and reaction is low, which is conducive to large-scale production; during the entire reaction process, no toxic and harmful substances are used or produced, which fully meets the requirements of clean production. ; The present invention improves the lattice oxygen activity on the surface of perovskite oxide through fluoride ion doping, exhibits excellent catalytic activity, and is suitable for improving the catalytic performance of fluorine-doped perovskite oxides prepared by different methods. The treatment method is simple, the catalyst's catalytic combustion performance for VOCs (especially toluene) is significantly improved, and it has good heat resistance and stable performance.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a comparison chart of the catalytic performance of LaMnO ₃ before and after fluorine ion doping in the embodiment of the present invention;

Figure 2 is a comparison chart of the catalytic performance of LaCoO ₃ before and after fluorine ion doping in the embodiment of the present invention;

Figure 3 is a comparison chart of the catalytic performance of LaFeO ₃ before and after fluorine ion doping in the embodiment of the present invention;

Figure 4 is a catalytic performance diagram of LaCoO ₃ doped with chloride ions and bromide ions in the comparative example of the present invention;

Figure 5 is a performance stability chart for toluene degradation of the 2.0 mmolF-doped LaCoO ₃ catalyst prepared in Example 6.

Detailed ways

Various exemplary embodiments of the invention will now be described in detail. This detailed description should not be construed as limitations of the invention, but rather as a more detailed description of certain aspects, features and embodiments of the invention.

It should be understood that the terms used in the present invention are only used to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges in the present invention, it should be understood that every intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or value intermediate within a stated range, and any other stated value or value intermediate within a stated range, is also included within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents relate. In the event of conflict with any incorporated document, the contents of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and changes can be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to the skilled person from the description of the invention. The specification and examples of the present invention are exemplary only.

The words "includes", "includes", "has", "contains", etc. used in this article are all open terms, which mean including but not limited to.

A preferred embodiment of the present invention, a method for activating lattice oxygen on the surface of a perovskite oxide, includes preparing a perovskite catalyst precursor doped with fluoride ions through a hydrothermal method, and preparing a perovskite catalyst in combination with heat treatment The specific steps are as follows:

S1. First add 0.005 mol of lanthanum nitrate and a certain amount of nitrate into the beaker. The nitrate is preferably cobalt nitrate, ferric nitrate or manganese nitrate; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol complexing agent, and finally add a certain amount of corresponding fluoride salt. The fluoride salt is cobalt fluoride, iron fluoride or manganese fluoride (the sum of the amounts of metal ions in the nitrate and the metal ion species in the fluoride salt (0.005mol), stir for 6h;

Specifically, through fluoride ion doping, the strong electron-attracting effect of fluoride ions is used to weaken the bond strength between transition metal ions and oxygen ions in the perovskite, promote surface lattice oxygen activation, and improve the catalytic combustion performance of the catalyst;

S2. Put the solution in the beaker that has been stirred for 6 hours in S1 into the reactor for hydrothermal reaction for 10 hours. After the hydrothermal reaction for 10 hours, dry the sample in the reactor at 80°C overnight to obtain the catalyst precursor;

S3. Place the catalyst precursor obtained in S2 in a muffle furnace and calcine it at a certain temperature for 2 hours at a certain heating rate to obtain a perovskite catalyst;

Preferably, the completely dried sample in S2 is ground into powder and placed in a muffle furnace.

The reaction equipment of the invention is simple, the reaction time is short, and the reaction is easy to operate; the reaction raw materials are easy to obtain, and the cost of raw materials and reaction is low, which is conducive to large-scale production; during the entire reaction process, no toxic and harmful substances are used or produced, which fully meets the requirements of clean production. ; The present invention improves the lattice oxygen activity on the surface of perovskite oxide through fluoride ion doping, exhibits excellent catalytic activity, and is suitable for improving the catalytic performance of fluorine-doped perovskite oxides prepared by different methods. The treatment method is simple, the catalyst's catalytic combustion performance for VOCs is significantly improved, and it has good heat resistance and stable structure.

As a preferred embodiment of the present invention, it may also have the following additional technical features:

In the embodiment of the present invention, the amount of fluoride salt added in step S1 is 10%-50% of the amount of lanthanum nitrate substance.

In the embodiment of the present invention, the complexing agent in step S1 is one or more of tartaric acid, citric acid and EDTA (ethylenediaminetetraacetic acid).

In the embodiment of the present invention, the temperature of the hydrothermal reaction in step S2 is 160-200°C.

In the embodiment of the present invention, the heating rate in step S3 is 2-10°C/min.

In the embodiment of the present invention, the calcination temperature of the catalyst precursor in step S3 is 700-1000°C.

In embodiments of the present invention, the perovskite catalyst has a cubic structure of _ABO3 .

The mass space velocity described in the present invention is defined as the standard volume flow rate of the reaction gas entering the reaction system per hour divided by the mass of the catalyst. Expressed in WHSV, unit mL·g ^-1 ·h ^-1 .

The toluene conversion rate described in the present invention is defined as the volume percentage of toluene converted into the reactor, that is, the difference in volume percentage of toluene in the incoming gas and the outgoing gas relative to the volume percentage of toluene in the incoming gas, unit %.

Example 1

First, add 0.005 mol of lanthanum nitrate and 0.004 mol of manganese nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent citric acid, add 1.0 mmol of manganese fluoride, and stir for 6 hours. Hydrothermal reaction was carried out in the kettle at 170°C for 10 hours. The sample in the reaction kettle was dried at 80°C overnight to obtain the catalyst precursor. The catalyst precursor was placed in a muffle furnace and calcined at 900°C for 2 hours at a heating rate of 2°C/min. Prepare 1.0mmol fluoride ion-doped LaMnO ₃ , press the powder into tablets, and grind it into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaMnO ₃ -1.0mmolF. Then, the catalytic combustion performance of toluene is evaluated. The evaluation conditions are: 100mg of catalyst was loaded into the reactor, the toluene concentration was 1000ppm, the synthetic air was the balance gas, the flow rate was 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 2

First, add 0.005 mol of lanthanum nitrate and 0.0035 mol of manganese nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent tartaric acid, add 1.5 mmol of manganese fluoride, stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 180°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 2°C/min and calcination at 800°C for 2 hours. 1.5mmol fluorine ion-doped LaMnO ₃ was pressed into tablets and ground into particles of 40 to 60 mesh. _The obtained catalyst was recorded as LaMnO ₃ -1.5mmolF. The toluene catalytic combustion performance was then evaluated. The evaluation conditions were: : 100mg catalyst is loaded into the reactor, the toluene concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 3

First, add 0.005 mol lanthanum nitrate and 0.003 mol manganese nitrate into the beaker; then add 20 mL deionized water to dissolve. After complete dissolution, add 0.04 mol complexing agent citric acid and EDTA (0.02 mol each), and add 2.0 mmol fluoride Manganese, stir for 6 hours, perform a hydrothermal reaction at 160°C in the reactor for 10 hours, dry the sample in the reactor at 80°C overnight to obtain the catalyst precursor, place the catalyst precursor in a muffle furnace, and heat up at a rate of 2°C/min , prepare 2.0mmol fluoride ion-doped LaMnO ₃ under the condition of calcination at 700°C for 2 hours, press the LaMnO ₃ powder into tablets, and grind it into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaMnO ₃ -2.0mmolF, and then catalyzes toluene. The combustion performance was evaluated. The evaluation conditions were as follows: 100 mg of catalyst was loaded into the reactor, the toluene concentration was 1000 ppm, the synthetic air was a balance gas, the flow rate was 100 mL·min ^-1 , and WHSV=60000 mL·g ^-1 ·h ^-1 . WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 4

First, add 0.005 mol of lanthanum nitrate and 0.004 mol of cobalt nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent EDTA, add 1.0 mmol of cobalt fluoride, stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 170°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 5°C/min and calcination at 900°C for 2 hours. 1.0 mmol fluoride ion-doped LaCoO ₃ . LaCoO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaCoO ₃ -1.0mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 5

First, add 0.005 mol of lanthanum nitrate and 0.0035 mol of cobalt nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent citric acid, add 1.5 mmol of cobalt fluoride, and stir for 6 hours. Hydrothermal reaction was carried out in the kettle at 180°C for 10 hours. The sample in the reaction kettle was dried at 80°C overnight to obtain the catalyst precursor. The catalyst precursor was placed in a muffle furnace and calcined at 800°C for 2 hours at a heating rate of 5°C/min. 1.5 mmol fluoride ion-doped LaCoO ₃ was prepared. LaCoO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaCoO ₃ -1.5mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 6

First, add 0.005 mol of lanthanum nitrate and 0.003 mol of cobalt nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent tartaric acid and EDTA (0.02 mol each), and add 2.0 mmol of cobalt fluoride. , stir for 6 hours, perform a hydrothermal reaction at 160°C in the reactor for 10 hours, dry the sample in the reactor at 80°C overnight, and obtain the catalyst precursor. Place the catalyst precursor in a muffle furnace with a heating rate of 5°C/min. 2.0 mmol of fluorine ion-doped LaCoO ₃ was prepared under calcination at 900°C for 2 hours. LaCoO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaCoO ₃ -2.0mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, and the flow rate is 100mL·min ^-1 . WHSV=60000mL·g ^-1 ·h ^-1 , WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 7

First, add 0.005 mol of lanthanum nitrate and 0.004 mol of iron nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent tartaric acid, add 1.0 mmol of ferric fluoride, stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 200°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 10°C/min and calcination at 1000°C for 2 hours. 1.0 mmol fluoride ion-doped LaFeO ₃ . LaFeO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaFeO ₃ -1.0mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 8

First, add 0.005 mol of lanthanum nitrate and 0.0035 mol of iron nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent EDTA, add 1.5 mmol of ferric fluoride, stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 170°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 10°C/min and calcination at 900°C for 2 hours. 1.5mmol fluoride ions doped LaFeO ₃ . LaFeO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaFeO ₃ -1.5mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Example 9

First, add 0.005 mol of lanthanum nitrate and 0.003 mol of ferric nitrate into the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agents tartaric acid and citric acid (0.02 mol each), and add 2.0 mmol of fluoride. Iron, stir for 6 hours, perform a hydrothermal reaction at 190°C in the reactor for 10 hours, dry the sample in the reactor at 80°C overnight, and obtain the catalyst precursor. Place the catalyst precursor in a muffle furnace with a heating rate of 10°C/min. , 2.0mmol fluoride ion-doped LaFeO ₃ was prepared under the condition of calcination at 900℃ for 2h. LaFeO ₃ powder was pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst was recorded as LaFeO ₃ -2.0mmolF. Then the catalytic combustion performance of toluene was evaluated. The evaluation conditions were: 100 mg of catalyst was loaded into the reactor, toluene The concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Comparative Example 1 Preparation of LaMnO ₃ without fluoride ion doping

Add 0.005 mol of lanthanum nitrate and 0.005 mol of manganese nitrate to the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent citric acid and EDTA (0.02 mol each), stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 160°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 2°C/min and calcination at 900°C for 2 hours. LaMnO ₃ that is not doped with fluorine ions; LaMnO ₃ powder is pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaMnO ₃ . Then the catalytic combustion performance of toluene is evaluated. The evaluation conditions are: 100 mg catalyst load Into the reactor, the toluene concentration is 1000ppm, the synthetic air is the balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Comparative Example 2 Preparation of LaCoO ₃ without fluoride ion doping

Add 0.005 mol of lanthanum nitrate and 0.005 mol of cobalt nitrate to the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent tartaric acid and EDTA (0.02 mol each), stir for 6 hours, and place in the reaction kettle Hydrothermal reaction was carried out at 170°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace, and the catalyst precursor was prepared at a heating rate of 5°C/min and calcination at 900°C for 2 hours. LaCoO ₃ doped with fluoride ions; press the LaCoO ₃ powder into tablets and grind it into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaCoO ₃ . Then the toluene catalytic combustion performance is evaluated. The evaluation conditions are: 100 mg of catalyst is loaded In the reactor, the toluene concentration is 1000ppm, the synthetic air is the balance gas, the flow rate is 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Comparative Example 3 Preparation of LaFeO ₃ without fluoride ion doping

Add 0.005 mol of lanthanum nitrate and 0.005 mol of ferric nitrate to the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent EDTA, stir for 6 hours, and conduct a hydrothermal reaction at 180°C in the reactor for 10 hours. Dry the sample in the reaction kettle overnight at 80°C to obtain the catalyst precursor. Place the catalyst precursor in a muffle furnace and prepare LaFeO ₃ without fluoride ions at a heating rate of 10°C/min and calcination at 900°C for 2 hours. ; LaFeO ₃ powder is pressed into tablets and ground into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaFeO ₃ . Then the toluene catalytic combustion performance is evaluated. The evaluation conditions are: 100 mg of catalyst is loaded into the reactor, and the toluene concentration is 1000ppm, synthetic air is balance gas, flow rate is 100mL·min ^-1 , WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Comparative example 4

Add 0.005 mol of lanthanum nitrate and 0.003 mol of cobalt nitrate to the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent citric acid, add 2.0 mmol of cobalt chloride, stir for 6 hours, and place in the reaction kettle A hydrothermal reaction was carried out at 180°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace and prepared at a heating rate of 2°C/min and calcination at 900°C for 2 hours. LaCoO ₃ doped with 2.0 mmol chloride ions; press the LaCoO ₃ powder into tablets and grind it into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaCoO ₃ -2.0 mmol Cl. Then the toluene catalytic combustion performance is evaluated. The evaluation conditions are: : 100mg catalyst is loaded into the reactor, the toluene concentration is 1000ppm, the synthetic air is balance gas, the flow rate is 100mL·min ^-1 , WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Comparative example 5

Add 0.005 mol of lanthanum nitrate and 0.003 mol of cobalt nitrate to the beaker; then add 20 mL of deionized water to dissolve. After complete dissolution, add 0.04 mol of the complexing agent EDTA, add 2.0 mmol of cobalt bromide, stir for 6 hours, and place in the reaction kettle Hydrothermal reaction was carried out at 180°C for 10 hours, and the sample in the reactor was dried at 80°C overnight to obtain a catalyst precursor. The catalyst precursor was placed in a muffle furnace, and the doped mixture was prepared at a heating rate of 2°C/min and calcination at 900°C for 2 hours. LaCoO ₃ mixed with 2.0 mmol bromide ions; press the LaCoO ₃ powder into tablets and grind it into particles of 40 to 60 mesh. The obtained catalyst is recorded as LaCoO ₃ -2.0 mmol Br. Then the catalytic combustion performance of toluene is evaluated. The evaluation conditions are: 100mg of catalyst was loaded into the reactor, the toluene concentration was 1000ppm, the synthetic air was the balance gas, the flow rate was 100mL·min ^-1 , and WHSV=60000mL·g ^-1 ·h ^-1 . The toluene catalytic combustion effect of the catalyst is shown in Table 1.

Table 1 Toluene catalytic combustion performance of catalyst

As can be seen from Table 1, the catalytic oxidation performance of VOCs of the perovskite oxide catalyst doped with fluoride ions in the present invention is significantly improved. In the activity evaluation of the catalyst provided by the present invention, its catalytic activity has been greatly improved. , T ₉₀ (the temperature at which the conversion rate is 90%) is reduced by up to 60°C compared to the untreated catalyst. It can also be seen from Example 9 and Comparative Examples 4-5 that the VOCs catalytic oxidation performance of the perovskite oxide catalyst doped with fluoride ions is also significantly higher than that of the perovskite oxide catalyst doped with chlorine and bromide ions. Mineral oxide catalyst. The comparison chart of the catalytic performance of LaMnO ₃ before and after fluorine ion doping in the embodiment of the present invention is shown in Figure 1. It can be seen from Figure 1 that the catalytic oxidation performance of VOCs of the LaMnO ₃ catalyst after fluorine ion doping is significantly higher than that of undoped fluorine. As the doping amount of fluorine ions increases, T ₉₀ (the temperature at which the conversion rate is 90%) also decreases, and the catalytic oxidation performance increases.

The catalytic performance comparison diagram of LaCoO ₃ before and after fluorine ion doping in the embodiment of the present invention is shown in Figure 2. It can be seen from Figure 2 that the catalytic oxidation performance of VOCs of the LaCoO ₃ catalyst after fluorine ion doping is significantly higher than that of undoped fluorine. However, when the doping amount of fluorine ions increases to 2.5 mmol, T ₉₀ (the temperature at which the conversion rate is 90%) begins to increase slightly, indicating that the doping amount of fluorine ions is not better. The best range is 1.0-2.0mmol;

The catalytic performance comparison diagram of LaFeO ₃ before and after fluoride ion doping in the embodiment of the present invention is shown in Figure 3. It can be seen from Figure 3 that the VOCs catalytic oxidation performance of the LaFeO ₃ catalyst after fluorine ion doping is significantly higher than that of the undoped LaFeO 3 catalyst. A catalyst for fluoride ions, and the doping amount of fluoride ions is in the range of 1.0-2.5mmol, the difference in T ₉₀ (the temperature at which the conversion rate is 90%) is not significant, and when the doping amount of fluoride ions increases to 2.5mmol, the T ₉₀ (The temperature at which the conversion rate is 90%) has also begun to increase slightly, indicating that the doping amount of fluorine ions is not better as much as 1.0-2.0mmol is the best;

The catalytic performance diagram of LaCoO ₃ doped with chloride ions and bromide ions in the comparative example of the present invention is shown in Figure 4. From Figure 4, it can be seen that the catalytic oxidation performance of the perovskite oxide catalyst doped with chloride ions and bromide ions is different in the catalytic oxidation performance of VOCs. Not significant, but significantly inferior to perovskite oxide catalysts doped with fluoride ions.

The toluene degradation performance stability diagram of the 2.0 mmol F-doped LaCoO ₃ catalyst prepared in Example 6 of the present invention is shown in Figure 5. It can be seen from Figure 5 that the toluene degradation performance of the F-doped perovskite oxide remains unchanged within 50 hours. It shows that it has excellent stability in catalytic degradation of toluene.

On the premise that no conflict occurs, those skilled in the art can freely combine and superimpose the above additional technical features.

The above-described embodiments only describe the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, those of ordinary skill in the art can make various modifications to the technical solutions of the present invention. All deformations and improvements shall fall within the protection scope determined by the claims of the present invention.

Claims (5)

1. The application of a perovskite oxide catalyst in catalyzing the combustion of VOCs is characterized in that the catalyst is prepared by a method for activating lattice oxygen on the surface of the perovskite oxide, and the method comprises the following steps:

s1, firstly mixing lanthanum nitrate and nitrate, adding water for dissolution, adding a complexing agent after complete dissolution, and finally adding fluoride salt, and stirring, wherein the addition amount of the fluoride salt is 10% -50% of that of lanthanum nitrate substances;

s2, carrying out hydrothermal reaction on the stirred solution in the step S1, and drying overnight after the hydrothermal reaction is finished to obtain a catalyst precursor, wherein the hydrothermal reaction temperature is 160-200 ℃ and the hydrothermal reaction time is 10 hours;

s3, calcining the catalyst precursor obtained in the S2;

the fluoride salt is cobalt fluoride, ferric fluoride or manganese fluoride.

2. The use of the perovskite oxide catalyst according to claim 1 for catalyzing the combustion of VOCs, wherein the nitrate is cobalt nitrate, iron nitrate or manganese nitrate.

3. The use of the perovskite oxide catalyst according to claim 1 for catalyzing the combustion of VOCs, wherein the complexing agent is one or more of tartaric acid, citric acid and EDTA.

4. The use of the perovskite oxide catalyst according to claim 1 for catalyzing the combustion of VOCs, wherein the calcination temperature is 700-1000 ℃ and the calcination time is 2 hours.

5. Use of the perovskite oxide catalyst according to claim 1 for catalyzing the combustion of VOCs, wherein the calcination process has a temperature rise rate of 2-10 ℃/min.